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    <center>Scilab Function</center>
    <div align="right">Last update : Jun 1997</div>
    <p>
      <b>sgrid</b> -  s-plane grid lines.  </p>
    <h3>
      <font color="blue">Calling Sequence</font>
    </h3>
    <dl>
      <dd>
        <tt>sgrid()  </tt>
      </dd>
      <dd>
        <tt>sgrid('new')  </tt>
      </dd>
      <dd>
        <tt>sgrid(zeta,wn [,color])  </tt>
      </dd>
    </dl>
    <h3>
      <font color="blue">Description</font>
    </h3>
    <p>
    Used in conjonction with evans, 
    plots lines of constant damping ratio (<tt>
        <b>zeta</b>
      </tt>)
    and natural frequency (<tt>
        <b>wn</b>
      </tt>).
  </p>
    <dl>
      <dd>
        <b>sgrid()</b>: add a grid over an existing continuous s-plane root with default values for <tt>
          <b>zeta</b>
        </tt> and <tt>
          <b>wn</b>
        </tt>.</dd>
      <dd>
        <b>sgrid('new')</b>: clears the graphic screen and then plots a default  s-plane grid</dd>
      <dd>
        <b>sgrid(zeta,wn [,color])</b>: same as <tt>
          <b>sgrid()</b>
        </tt> but uses the provided damping ratio and  natural frequency.</dd>
    </dl>
    <h3>
      <font color="blue">Examples</font>
    </h3>
    <pre>

H=syslin('c',352*poly(-5,'s')/poly([0,0,2000,200,25,1],'s','c'));
evans(H,100)
sgrid()
sgrid(0.6,2,7)
 
  </pre>
    <h3>
      <font color="blue">See Also</font>
    </h3>
    <p>
      <a href="evans.htm">
        <tt>
          <b>evans</b>
        </tt>
      </a>,&nbsp;&nbsp;</p>
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